The present invention relates to mattress structures and particularly to a mattress structure having a foam mattress core. The mattress structure may be configured as a stand-alone unit for use on any deck for a bed or the mattress structure may be configured for use with an associated base. More particularly, the present invention relates to a mattress structure having a foam core that is shaped and configured to provide support and firmness characteristics similar to those provided by mattresses having air bladders.
It is well know to provide foam support pads or mattresses for supporting a user reclining on the pad. For example, U.S. Pat. Nos 4,879,776; 5,038,433; 5,077,849; 5,111,542; and 5,172,439, all to Farley, disclose mattress overlays and pads for supporting a user. In addition, U.S. Pat. Nos. 4,449,261 to Magnusson and 4,991,244 to Walker disclose mattress borders for receiving core mattresses and U.S. Pat. Nos. 5,105,488 to Hutchinson et al.; 4,803,744 to Peck et al.; and 4,424,600 and 4,435,864 to Callaway disclose supporting surfaces having selectively adjustable firmness. Finally, U.S. patent application Ser. No. 08/565,409 to Washburn et al. filed Nov. 30, 1995 and assigned to an affiliate of the assignee of the present invention, the specification of which is herein incorporated by reference, discloses a mattress kit and mattresses constructed therefrom that can include a plurality foam core elements
What is needed is a mattress structure having a foam core provided with longitudinally spaced and transversely extending zones providing the support and firmness characteristics typically provided by a mattress including a core having longitudinally spaced-apart air bladders. In addition, users would appreciate such a mattress having a foam mattress core of unitary construction and which is compatible with a bed having an articulating deck. Such a mattress should also include a mechanism for minimizing the sheer forces directed against the user when the bed carrying the mattress articulates.
According to the present invention, an elongated mattress core for a mattress structure is provided. The mattress core includes a foam core. The foam core has an upwardly-facing top surface, a bottom surface spaced apart from the top surface, and first and second spaced-apart elongated sides connecting the top and bottom surfaces.
The foam core is formed to include a plurality of longitudinally spaced-apart transverse slits extending downwardly from the top surface. Each slit terminates at a lower end which is spaced apart from the bottom surface by a first distance. In addition, each slit extends transversely from a first slit end spaced apart from the first side of the foam core to a second slit end spaced apart from the second side of the foam core. Each adjacent pair of slits defines a foam column. Thus, the foam core has a plurality of longitudinally spaced apart and transversely extending foam columns, each foam column having a pair of generally vertical column side walls defining the slits.
In preferred embodiments, the mattress structure includes a mattress cover defining an interior region and a foam core received in the interior region. A shear layer made from a material having a low coefficient of friction preferably covers the top and sides of the foam core and is positioned between the foam core and the mattress cover so that the mattress cover can slide relative to the foam core. Thus, if the mattress structure is used on a bed having an articulating deck, the mattress cover can slide relative to the foam core as the deck articulates to minimize the shear forces acting between the mattress cover and the user during articulation of the deck and mattress structure and instead expend those shear forces by having the mattress cover slide relative to the foam core.
The foam core also includes a plurality of longitudinally spaced apart and transversely extending foam columns. Each foam column includes a top, a bottom, and generally vertically extending and transversely extending side walls connecting the top and the bottom. The side walls of adjacent foam columns cooperate to define a plurality of longitudinally spaced-apart and transversely extending slits.
The side walls of each foam column include a low-friction coating so that each column can compress and decompress without being hindered by drag forces resulting from frictional engagement with adjacent foam columns. Preferably, the low-friction coating is a fabric or material having a low coefficient of friction which is received by the slit defined by the adjacent side walls of adjacent foam columns. Thus, the unitary foam core is in effect provided with longitudinally spaced-apart zones of foam that operate independently to provide the mattress structure with longitudinal zones similar to the zones that can be provided by air bladders.
As mentioned above, the foam core is of unitary construction. In addition, however, the foam core can be configured so that the firmness and support characteristics of each foam column is individually selected prior to manufacture. Individually selecting the support and firmness characteristics of each foam column of the mattress structure allows the mattress structure to provide support and firmness characteristics that vary along the length of the sleeping surface of the mattress structure. Having varied support and firmness characteristics allows the mattress structure to achieve a profile along the length of the mattress structure of support and firmness characteristics similar to the support and firmness characteristics that can be provided by a mattress structure having a plurality of air bladders.
The mattress structure in accordance with the present invention can be provided in a xe2x80x9cstand-alonexe2x80x9d first embodiment for use on any bed deck or other generally horizontal surface or a second embodiment including a separate base for supporting the mattress. With each embodiment, the foam core includes a foam frame made from relatively stiff foam bonded to a perimeter defined by the plurality of foam columns. In the first embodiment, the entire frame is attached to the plurality of columns. In the second embodiment, the frame includes an upper portion attached to the plurality of columns and a lower portion attached to the base to form a base frame so that the second embodiment of the mattress structure provides the advantages of a step deck and a mattress for a step deck as described in U.S. patent application Ser. Nos. 08/511,546 to Kramer et al. and 08/511,547 to Weismiller et al., both filed on Aug. 4, 1995 and both assigned to an affiliate of the assignee of the present invention.
Additional objects, features and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of the preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.